1. Field of the Invention
This invention relates generally to diode pumped laser systems, and more particularly, to diode pumped laser systems with feedback control that includes diagnostics.
1. Description of the Related Art
It is desirable to be able to directly monitor various performance parameters of a diode pumped laser system. These performance parameters can include, but are not limited to, (i) power output, (ii) optical activity or output, (iii) wavelength detection and tuning indications, (iv) laser operation data of the pumped laser using light traveling back from the laser medium in the cavity to the diode pump source, (v) pulse output characteristics of pulse-driven diode pump sources and (vi) feedback from damaged optical fiber links for detection and diagnostic purposes.
Coupling optics have been used for coupling output emissions of a laser diode pump source to an optical fiber. An example of such a coupling optics is disclosed in U.S. Pat. No. 5,127,068; the "'068 patent", incorporated herein by this reference. In one embodiment disclosed in the '068 patent, radiation emitted from a laser diode bar, with a plurality of emitters, focused into multi-mode optical fibers, which may be part of an optical fiber bundle, includes placing coupling optics between the emitting facets of emitters, and the ends of the multi-mode optical fibers. The coupling optics can be a piece of a multi-mode optical fiber which can extend along the length of a diode bar pump source. The coupling optics is carefully positioned with respect to the output facets of the laser diode bar in order to properly collimate them. This is accomplished by aligning and securing it in place with a suitable epoxy.
Current diagnostic methods for such a system today are achieved by placing a beam sampling device in the path of the emitted light between the diode pump source and the coupling optics. This method presents two problems, (i) the distance between the diode pump source and the coupling optics is about 20 microns, and (ii) placing the sampling device in the path of the emitted light uses a good portion of the available light which is normally focused into the laser medium for pumping purposes. An example of a suitable sampling device is a beam splitter. Additionally, it is mechanically difficult to position a sampling device between the two elements. If the problem of limited space is ignored, building a feedback system would require extra mechanical components for stability. Such stability adds complexity to the feedback system and decreases the optical power output that is available from the laser diode source.
It would be highly desirable to provide a feedback system is much simpler than those currently proposed. There is a need for a feedback system that would not occupy the limited space, (i) between the diode pump source and the coupling optics or (ii) the coupling optics and fiber bundle or laser medium, and which does not use light intended for use in pumping the laser medium as part of the feedback system.